Insulator



Feb. 12, 1929.

c. s GORDON INSUL'ATOR Filed July l, 1925 INVENTOR 6'. (5' 00111010 1ATTORNEY h UNITED" STATES I onnsmins. oonnon, or raw Yonx, N. Y.,assrcnon -PV.:ATEN 'IAOFFICEI.I I

TO AMERICAN TELEPHONE-AND TELEGRAPH COMPANY, A CORPORATION OF NEW YORK.

- msum'ron.

' Application filedluly 1,

1 This invention relates improvements in insulators, and moreparticularly to a construction of insulator adapted to stabihze theleakage loss under diflerent weather condif With the developmentofmethods of transmitting telephonic and telegraphic s gnals by means ofcarrier currents propagated alon' open wire lines, new transm ssion probems have been introduced. Owing to the fact that the carrier currentsemployed are relatively high in frequ as compared if with the voicecurrents or orse currents utilized in the ordinary methods ofcommunication, it has been found that the attenuation is ver 'markedlyincreased, so much so, in fact, t at repeaters for amplifying thetransmitted currents mustbe separated by much shorter distances, therebyadding tothe ex-- pense of the plant outside the 'terminalstations atwhich" the carrier apparatus is applied, 1 A ver material part of thisattenuation is 1 due to eakage loss through the insulators comprisingthe other plate.

thus formed introduces a leakage loss due to which are customarilyemployed upon open wire lines, and this loss varies through a very widerange under difierentweather conditions. The insulator acts like acondenser, the glass of the insulator constituting the dielectric, theline wire and tie-wire on the outside of the insulator comprisingone'plate, and the wooden pin upon which the insulator is supported Thecondenser so-called dielectric hysteresis and this loss varies with thecapacity of the condenser.

In dry weather, the outer plate of the condenser, that is, the portionof the line wire adjacent to the insulator and its associated tie wire,constitutes a'plate of relatively small. area so that the capacity isrelatively small and hence the leakage loss, even at carrier fre-'quencies, is small'as compared with the total attenuation of the,circuit. Durin wet weather, however, the entire outer sur ace of theinsulator becomes wet, with the result that the conductive area externalto the insulator is very much increased. As a result the capacity, andconsequentl the leakage loss, is very much increased. uring the extremesof wet and dry weather the attenuation of the system varies through awide range due to -the position of the pin in Figure 1925.; Serial No.40,893.

this cause alone, and this vision of special regul ting apparatus formaintaining the transmission equivalent'of the circuit constant underall weather conditions. 1

In order to avoidlthe expense ofthe regu lating arrangements it becomesdesirable to devise some method for stabilizing the capacity of theinsulator and hence its dielectricloss represent two embodiments of theinvention,

and Fig. 1* represents the supporting pinto be used in connection withthe insulators of Fi s. 1 and 2.

eferring to Fig. l, A designates a body of dielectric material having aninternall screw-threaded opening 11 by means of whic the body may bescrewed upon asupporting in. A petticoat l2extendsdownwardly from v thebody A and surrounds the supporting pinv ecessitates the prosome littledistance away from its outer sur- I face as shown by the dotted linerepresenting 1. The in- ,ner surface of the petticoat is corru ated, asshown at 13, to increase the lengt dry ath formed by 7 crab thesecorrugationswill be made in the form of a screw thread of the same pitchas the internal threads of the openin 11 so that the mold or core whichis used in Eorming the entire body'may be screwed out after the plasticmaterial has hardened.

Instead of securing the line conductor and of the said 1nner surface.Preftie wire about the outer margin of the dielectric body A, as in theusual type of insulator, a small knob 14.- is formed on the top of theinsulator so that the line conductor and tie wire may be, seated in.the'peripheral groove 15 of the knob. A laterally extending,umbrellalike structure 16 is provided near the upper edge of thedielectric body A to maintain the outer surface of the dielectric bodydry bescrew -threaded opening 11.

- {principal existing. capacity neath the structure 16 downto a pointsubstantially opposite the lower edge of' the In order to fix orstabilize the leakage loss, which'is proportionate to the capacity, acoa mg -"outer surface of the petticoat 12 will not materially increasethe'capacity .as this conductive area is-isolate'd from the lineconductor and tie wire and theassociated, conductive material 17 bya'dry path due to the corrugations 18 on the under side of theumbrella-like struc- -ture 18, and is likewise isolated from thesupportlng pin by the dry path'due tp the corrugations 13. 5

'Obviousl therefore, thecapacity of the insulator and hencethe'dielectric loss (which is proportionate to the capacity) isfixed andstablllzed at a value somewhat greater than the dry weather value whichwould exist if there were no conductive layer 17, but yet materiallysmaller than the value that would,

exist duringwet weather if it were possible for the whole-externalsurface of the insulater to become wet.. Also, the direct cur-l rentleakage is stabilized at a low value condition by the provision of thelong dry path under the petticoat of1the insulator. It is unnecessary toprovide any additional repeaters by reason of the useof the outermetallic' shell, as repeaters "must be provided even with existinginsulators to give sufiivcient gain for the worst transmissionconditions. By stabilizing the insulator-at an intermediate condition,however, some saving in the number of repeaters may be possible, but,what is more important, the equipment for 'maintaining the transmissionconstant maybe eliminated and the expense propo-r-' tlonately cut down.

Fig. 2 shows a slight modification of the arrangement of Fig. 1. I Inthis instance the knob or button 1%, instead of being coated or coveredwith aconductive material, is 1tself formed of conductive material-whichmay be welded, soldered, riveted or otherwisesecured to the conductivelayer 17. The

underlying principles of this structure are, however, the same as in thecase of Fig. 1 and no further discussion is necessary.

It will be obvious that the general prinof conductive material 17 isapplied to the I outer surface of the dielectric over the knob 14 andover the parts of the umbrella-like. -structure 16' which are exposed tothe weather.

Owing to the shape of the structure 16, the

surfaceand the pin,

ciplesherein disclosed may be embodied in many other organizationswidely different from those illustrated without departing from thespirit of the invention as defined in the appended claims.

What is claimed is:.

1. An insulator comprising a body of dielectric material havingan inneropening to receive a supporting pin, a relatively small button likestructure on the top of said body having a grooved portion ,to which theline conductor and tie wire may be secured, said grooved portion beingof a diameter not materially greater than the supporting pin, anumbrella-like structure at the upper side of said dielectric body forprotecting a ortion of the outerasurface of said bo y om moisture, and asurface of conductive material extending from'the outer edgesof saidumbrella-like structure to and over said button, the umbrella-likestructure with its ,metallic surface extending; horizontally utthe topof cured, said grooved" portion being of a diam eter not materiallygreater than the supporting pin, "an umbrella-like structure at theupper side of said dielectric body for protecting a portion ofthe outersurface of said body from moisture, anda surface of conductive materialextending. from thenuter edges of said umbrella-like structure toandover said button, the umbrella-likev structure with its metallic surfaceextending horizontally outward and away to reduce the capacity-betweenthe metallic surface and the pin, and the underside of saidumbrella-like structure being corrugated to lengthenthe dry'path formedthereby.

3. An insulator comprising a body of dielectric material havingan inneropening to receive a supporting pin, a relatively small button-likestructure on the top of said body the line conductor-and tie wire may besecured, said grooved portion being of a diameter not materially greaterthan the supporting pin, an umbrella-like structure at the upper side ofsaid dielectric body for-protecting a portion of the outer surface ofsaid body from moisture, a surface of conductive material extending fromthe outer edges of said umbrella-like structure to and over sald fromthe supporting pm '11s having a grooved portion to which button, theumbrella-like structure with its metallic surface extending horizontallyoutward and away, fromthe supporting pin to reduce the capacity betweenthe metallic and a petticoa't extendthe supporting pin.

' from said ing downwardly .from said dielectric and surrounding butspaced away from the threadedopening to receive a supporting pin and atticoat extending downwardly &(ly and surrounding the-pin,

the inner surface of said Petticoat having screw-threaded corrugationsof i the same pitch but of larger diameter than the threads of the pin,whereby an integral mold may 15 be used to form-thetwo sets of threadson the inner'surface of the insulator and the moldmaybe unscrewed fromthe interior of the insulator.

In testimony whereof, I have signed my 20 name to this specificationthis 25th day of June, 1925.

CHESTER s. :GORDON.

